Chapter 3 SPAN Operation
OEM7 SPAN Installation and Operation User Manual v14
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The offset between the antenna phase center and the IMU axis must remain constant and be known accur-
ately (m). The X, Y and Z directions are clearly marked on the IMU enclosure. The SETINSTRANSLATION
parameters are (where the standard deviation fields are optional and the distances are measured from the
IMU to the antenna):
ANT1 x_offset y_offset z_offset [x_stdev] [y_stdev] [z_stdev]
This example shows a mounting configuration with a negative X offset, negative Y offset and
positive Z offset.
A typical RTK GNSS solution is accurate to a few centimeters. For the integrated GNSS+INS system to
have this level of accuracy, the offset must be measured to within a centimeter. Any offset error between the
two systems shows up directly in the output position. For example, a 10 cm error in recording this offset will
result in at least a 10 cm error in the output.
If it is impossible to measure the IMU to GNSS antenna offset precisely, the offset can be estimated by car-
rying out the Lever Arm Calibration Routine. See
4. Issue the
SETINSROTATION
command, using the
RBV
parameter, to enter the Euler Angle rotation from
the IMU Body frame to the Vehicle frame. See the
SETINSROTATION
command in the
for more information.
Accurate knowledge of the rotational offset between the IMU Body frame and the Vehicle frame (the RBV
rotation) is critical to correctly computing an attitude solution, and is required before a Kinematic alignment is
possible.
The SETINSROTATION parameters are (where the standard deviation fields are optional):
RBV x_rotation y_rotation z_rotation [x_stdev] [y_stddev] [z_stdev]
The order of rotations is Z-X-Y. All rotations are right handed.
